Graft polymers with controlled viscosity

Abstract

The present invention relates to a process for the preparation of graft thermoplastic polymers in which at least one thermoplastic polymer (A) is grafted with a functional monomer in the presence of a substance which inhibits or reduces the crosslinking or the depolymerization of (A). This substance may be a stable nitroxide radical. Graft polymers are useful as compatibilizing agents in mixtures of polymers and as coextrusion binders. The invention also relates to multilayer structures including these binders.

I claim: 
     
       1. Process comprising preparing graft thermoplastic polymers in which at least one thermoplastic polymer (A) being grafted with a functional monomer in the presence of a substance which inhibits or reduces the crosslinking or the depolymerization of (A). 
     
     
       2. Process according to claim 1, wherein the substance that inhibits or reduces the crosslinking or the depolymerization of (A) is a stable nitroxide radical including the group ═N--O. 
     
     
       3. Process according to claim 1, wherein the polymer (A) is selected from the group consisting of polyethylenes, polypropylenes, polybutenes and polystyrenes, these polymers being homo- or copolymers. 
     
     
       4. Process according to claim 1, wherein the functional monomer is maleic anhydride. 
     
     
       5. Process according to claim 1, wherein the quantity of stable nitroxide radical is between 0.05 and 200 millimoles per kg of polymer (A). 
     
     
       6. Process according to claim 5, wherein the quantity is between 0.1 and 10.